1. Field of the Invention
This invention relates to apparatus for cleaning the interior of tubular elements such as are used in tube bundle heat exchanger assemblies and the like. More specifically, this invention relates to cleaning such tubular elements using a reciprocating, fluid-driven cleaning lance.
2. Description of the Prior Art
Tubing and tube bundles, particularly those in heat exchangers, generally require periodic cleaning. Fluid pressure tube cleaning apparatus in general were disclosed in U.S. Pat. Nos. 620,224; 2,494,380; 3,246,660; 3,269,659; 3,377,026; 3,589,388; 3,736,909; 3,794,051; 3,817,262; 3,901,252; 3,903,912; 3,938,535 and 3,987,963. It is also known to use a reciprocating fluid driven lance having one or more nozzles for directing cleaning fluid under pressure at the interior passageway of the tubing to dislodge foreign substances and clean the tubing. Such fluid pressure tube cleaning systems were disclosed in U.S. Pat. Nos. 3,246,847; 3,791,583; and 4,137,928 (which is owned by applicant). An improved reciprocating lance apparatus having a novel means for dampening the reciprocating motion of the lance was disclosed in U.S. Pat. No. 4,344,570 of which applicant is the inventor.
Reciprocating lance cleaning apparatus generally included a hollow lance portion and a piston portion. The lance portion typically had a spray nozzle at one end for directing the cleaning fluid to the interior of the tubes, and the piston portion was adapted for reciprocating motion in a tubular housing in response to fluid pressure differentials acting in alternating fashion upon one or more piston surfaces. Such systems were disclosed for example in U.S. Pat. Nos. 4,137,928 and 4,344,570. In these systems, the lance housing included a controllable pressurized fluid inlet at the forward end of the housing and a controllable fluid outlet near the rear of the housing. The lance was driven back and forth in the housing by controlling the inlet and outlet valves to alternately create a pressure differential in front and behind the piston portion of the lance. One problem which developed in the operation of these prior systems was that if the system was stopped when the lance was in the rear most portion of the housing, it was difficult if not impossible for the driving fluid to reach and act upon the rear face of the piston or enter the interior of the lance so that normal reciprocal operations could resume.
Other lance cleaning systems included threaded surfaces upon the lance body or the piston portion to cause the lance to rotate about its longitudinal axis in response to fluid dynamics acting upon the threaded surfaces. Such systems were disclosed in U.S. Pat. Nos. 4,137,928 and 4,344,570. In these systems, a single lead raised, threaded portion of the lance body or piston was fitted relatively snugly within the tubular lance housing. Consequently, substantially all of the fluid traversing the exterior of the lance body was forced to flow in the grooved path created between the threaded portion of the piston and the interior of the tubular housing. These systems suffered problems in delivering adequate rotational and translational movement of the lance. Further, no provision was made to vary or control the rotational or transverse speed of the lance.